142 T. C. CHAMBERLIN 



and perhaps more effective on the whole than fragmentation. 

 This would quite surely be true of the minute particles. According 

 to the interpretation of Bell/ a milling process of this triturative 

 sort has proved very effective in reducing to minute sizes the 

 satelUtesimals of the Saturnian rings. When masses of any con- 

 siderable size were reached, probably exfoliation from the effects of 

 rotation in the unscreened rays of the sun would give rise to flaking 

 and thus prepare new matter for the milling process. 



On the other hand, if magnetic particles were much developed, 

 it is probable that their special attraction would aid in building 

 up masses, so far as the supply of such material went. Probably 

 such malleable substances as iron, nickel, and the other metals 

 would weld rather freely by impact. Metallic particles might 

 thus unite nearly to the extent they were permitted to come into 

 collision. Such stony substances as brought crystalline or con- 

 cretionary forces into play would probably build up more readily 

 than other matter and more effectively resist destructive agencies 

 afterward. But it must be noted in all these cases that as the 

 molecules were more or less heterogeneously mixed originally, 

 the opportunities for assembhng homogeneous matter to form 

 aggregates of any one kind w6uld have natural limitations. 



The logic of the case, taken all together, seems to lead to the 

 conclusion that aggregates arising under these ideal planetesimal 

 conditions would be limited to small sizes as a general rule. This 

 is in harmony with the results realized in the Saturnian rings, and 

 also in the zodiacal planetesimals to be more fully discussed in the 

 next article. It is also in harmony with the dimensions attained 

 by the chondri and chondrules that form characteristic constituents 

 of 90 per cent of the stony meteorites. These range in size from a 

 walnut down to spherules of dustlike minuteness.^ 



The point of most critical importance to our inquiry is the 

 effect on selective action introduced by these growths .so far as 

 th':''' went. In the first place, all such matter as continued in 

 a free molecular state, whether aggregated as gases or deployed as 

 planetesimals, would not be gathered about these small aggregates 



' Loc. cit. 



^ O. C. Farrington, Meteorites (1915), p. 102. 



